1. Field of the Invention
The present invention relates to a solid-state imaging element and a solid-state imaging device, and particularly has an improved characteristic in an arrangement for connecting electrodes of vertical transfer registers in a solid-state imaging element to bus lines for inputting predetermined drive signals to the respective electrodes.
2. Description of the Related Art
An existing charge-coupled device (CCD) solid-state imaging element used in a solid-state imaging device includes, on a semiconductor substrate, plural light-receiving elements arranged vertically and horizontally, plural vertical transfer registers provided adjacent to these light-receiving elements, and a horizontal transfer register provided along one side of the rectangular pixel region in which these vertical transfer registers and light-receiving elements are provided.
Charges that are accumulated in the respective light-receiving elements in response to light reception thereof are read out by the vertical transfer registers so as to be vertically transferred through the vertical transfer registers to the horizontal transfer register, followed by being horizontally transferred by the horizontal transfer register. The transferred charges are converted into an electric signal (voltage signal, in many cases) and amplified in an output part provided downstream of the horizontal transfer register, so that a requisite image signal is produced and output.
Specifically, as schematically shown in FIG. 6, vertical transfer registers 120 are provided in such a manner as to be adjacent to light-receiving elements 110 arranged vertically and horizontally in a pixel region 100 and be extended in the upward and downward directions in FIG. 6. Furthermore, a horizontal transfer register 130 is provided in such a manner as to be connected to ends of the vertical transfer registers 120 and be extended in the left and right directions in FIG. 6.
In general, the vertical transfer registers 120 are driven by four-phase vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4. In the pixel region 100, vertical transfer electrodes 210 that are extended in the lateral direction and are supplied with the respective vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4 are arranged continuously across the vertical direction. Furthermore, necessary bus lines 150 provided outside the pixel region 100 are connected to the respective vertical transfer electrodes 210, and the vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4 are input to the respective vertical transfer electrodes 210 via the bus lines 150.
In addition, the horizontal transfer register 130 is driven by two-phase horizontal drive signals Hφ1 and Hφ2 in general. Across the horizontal transfer register 130, horizontal transfer electrodes 310 to which the respective horizontal drive signals Hφ1 and Hφ2 are input are continuously arranged. Furthermore, necessary bus lines 150′ provided outside the pixel region 100 are connected to the respective horizontal transfer electrodes 310, and the horizontal drive signals Hφ1 and Hφ2 are input to the horizontal transfer electrodes 310 via the bus lines 150′.
Due to input of the vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4 to the respective vertical transfer electrodes 210 and input of the horizontal drive signals Hφ1 and Hφ2 to the respective horizontal transfer electrodes 310, potentials for forwarding the charges in a bucket brigade manner are formed in the vertical transfer registers 120 and the horizontal transfer register 130, and thereby the charges accumulated in the respective light-receiving elements 110 can be transferred.
The vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4 and the horizontal drive signals Hφ1 and Hφ2 are produced by a timing generator, and are input to the bus lines 150 and 150′ via vertical drive signal inputs 140 and horizontal drive signal inputs 170, respectively, that are formed of signal input terminals of the solid-state imaging element. The number of the vertical drive signal inputs 140 is four because the four-phase vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4 are input, while the number of the horizontal drive signal inputs 170 is two because the two-phase horizontal drive signals Hφ1 and Hφ2 are input.
In such a solid-state imaging element, the vertical transfer electrodes 210 have a comparatively long length because they are formed to traverse the pixel region 100. Therefore, in order to suppress deterioration of the vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4, as shown in FIG. 7, both the ends of the vertical transfer electrodes 210 are protruded from the pixel region 100 and connected to the bus lines 150 so that the vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4 are input to both the ends. In this configuration, the bus lines 150 are provided in such a manner as to surround the pixel region 100 (e.g., refer to Japanese Patent Laid-Open No. 11-40795).
In recent years, due to requirements for solid-state imaging devices to have higher performance, the number of light-receiving elements 110 provided in a solid-state imaging element has been dramatically increasing. Therefore, the time period it takes for signal charges accumulated in the light-receiving elements 110 to be read out and transferred has been becoming longer than ever before.
To address this, a solid-state imaging element in which two horizontal transfer registers 130 sandwich the pixel region 100 as schematically shown in FIG. 8 has also been devised in order to enhance the speed of reading-out processing.
However, if the horizontal transfer registers 130 are provided on the upper and lower sides of the pixel region 100 as shown in FIG. 8, it is difficult for the bus lines 150 to be wired along the left, upper and right sides of the pixel region 100 so as to surround the pixel region 100 as shown in FIG. 7.
Therefore, in the solid-state imaging element shown in FIG. 8, necessary vertical drive signal inputs 140 are provided near the ends of the vertical transfer electrodes 210 and the vertical drive signals Vφ1, Vφ2, Vφ3, and Vφ4 are input thereto. In this configuration, it is requisite to ensure, in the bus lines 150, a part for connection to the drive signal inputs 140 in an area other than the area corresponding to the part that is near the pixel region 100 and used for connection to the respective vertical transfer electrodes 210.
To satisfy this requirement, as shown in FIG. 8, fold-back parts are formed in the bus lines 150 so that the bus lines 150 are wired into a loop shape and connected to the drive signal inputs 140.